A Baboon Brain Atlas for Magnetic Resonance Imaging and Positron Emission Tomography Image Analysis

The olive baboon (Papio anubis) is phylogenetically proximal to humans. Investigation into the baboon brain has shed light on the function and organization of the human brain, as well as on the mechanistic insights of neurological disorders such as Alzheimer’s and Parkinson’s. Non-invasive brain imaging, including positron emission tomography (PET) and magnetic resonance imaging (MRI), are the primary outcome measures frequently used in baboon studies. PET functional imaging has long been used to study cerebral metabolic processes, though it lacks clear and reliable anatomical information. In contrast, MRI provides a clear definition of soft tissue with high resolution and contrast to distinguish brain pathology and anatomy, but lacks specific markers of neuroreceptors and/or neurometabolites. There is a need to create a brain atlas that combines the anatomical and functional/neurochemical data independently available from MRI and PET. For this purpose, a three-dimensional atlas of the olive baboon brain was developed to enable multimodal imaging analysis. The atlas was created on a population-representative template encompassing 89 baboon brains. The atlas defines 24 brain regions, including the thalamus, cerebral cortex, putamen, corpus callosum, and insula. The atlas was evaluated with four MRI images and 20 PET images employing the radiotracers for [11C]benzamide, [11C]metergoline, [18F]FAHA, and [11C]rolipram, with and without structural aids like [18F]flurodeoxyglycose images. The atlas-based analysis pipeline includes automated segmentation, registration, quantification of region volume, the volume of distribution, and standardized uptake value. Results showed that, in comparison to PET analysis utilizing the “gold standard” manual quantification by neuroscientists, the performance of the atlas-based analysis was at >80 and >70% agreement for MRI and PET, respectively. The atlas can serve as a foundation for further refinement, and incorporation into a high-throughput workflow of baboon PET and MRI data. The new atlas is freely available on the Figshare online repository (https://doi.org/10.6084/m9.figshare.16663339), and the template images are available from neuroImaging tools & resources collaboratory (NITRC) (https://www.nitrc.org/projects/haiko89/).

An ancestral genomic sequence that serves as a nucleation site for de novo gene birth

A short non-coding sequence present between the gamma-glutamyltransferase 1 (GGT1) and gamma-glutamyltransferase 5 (GGT5) genes, termed a spacer sequence has been detected in the genomes of Mus musculus, the house mouse and in Philippine tarsier, a primitive ancestral primate. It is highly conserved during primate evolution with certain sequences being totally invariant from mouse to humans. Evidence is presented to show this intergenic sequence serves as a nucleation site for the initiation of diverse genes. We also outline the birth of the human lincRNA gene BCRP3 (BCR activator of RhoGEF and GTPase 3 pseudogene) during primate evolution. The gene developmental process involves sequence initiation, addition of a complex of tandem transposable elements and addition of a segment of another gene. The sequence, initially formed in the Old World Monkeys such as the Rhesus monkey (Macaca mulatta) and the baboon (Papio anubis), develops into different primate genes before evolving into the human BCRP3 gene; it appears to also include trial and error during sequence/gene formation. The protein gene, GGT5 may have also formed by spacer sequence initiation in an ancient ancestor such as zebrafish, but spacer and GGT5 gene sequence drift during evolution produced a divergence that precludes further assessment.

Age- and sex-related differences in baboon (Papio anubis) gray matter covariation

Age-related changes in cognition, brain morphology, and behavior are exhibited in several primate species. Baboons, like humans, naturally develop Alzheimer's disease-like pathology and cognitive declines with age and are an underutilized model for studies of aging. To determine age-related differences in gray matter covariation of 89 olive baboons (Papio anubis), we used source-based morphometry (SBM) to analyze data from magnetic resonance images. We hypothesized that we would find significant age effects in one or more SBM components, particularly those which include regions influenced by age in humans and other nonhuman primates (NHPs). A multivariate analysis of variance revealed that individual weighted gray matter covariation scores differed across the age classes. Elderly baboons contributed significantly less to gray matter covariation components including the brainstem, superior parietal cortex, thalamus, and pallidum compared to juveniles, and middle and superior frontal cortex compared to juveniles and young adults (p<0.05). Future studies should the relationship between the changes in gray matter covariation reported here and age-related cognitive decline.

Ecological and social pressures interfere with homeostatic sleep regulation in the wild

Sleep is fundamental to the health and fitness of all animals. The physiological importance of sleep is underscored by the central role of homeostasis in determining sleep investment – following periods of sleep deprivation, individuals experience longer and more intense sleep bouts. Yet, most studies of sleep have been conducted in highly controlled settings, disconnected from the ecological and social context that may exert pressures on sleep patterns in conflict with homeostatic regulation. Using tri-axial accelerometry and GPS to track the sleep patterns of a group of wild baboons (Papio anubis) at multiple temporal and spatial scales, we found that ecological and social pressures indeed interfere with homeostatic sleep regulation. Baboons sacrificed time spent sleeping when in less familiar locations and when sleeping in proximity to more group-mates, regardless of how much they had slept the prior night or how much they had physically exerted themselves the preceding day. Moreover, we found that the collective dynamics characteristic of social animal groups persist into the sleep period, as baboons exhibited synchronized patterns of waking throughout the night, particularly with nearby group-mates. Thus, for animals whose fitness depends critically on avoiding predation and developing social relationships, maintaining sleep homeostasis may be only secondary to remaining vigilant when sleeping in risky habitats and interacting with group-mates during the night. Our results highlight the importance of studying sleep in ecologically relevant contexts, where the adaptive function of sleep patterns directly reflect the complex trade-offs that have guided its evolution.

Species Composition, Diversity, and Habitat Association of Medium- and Large-Sized Mammals in Chimit-Kolla, Abay Gorge, Ethiopia

Identifying the species distribution, diversity, and habitat association provides input to launch proper conservation interventions. A survey of medium- and large-sized mammal species was conducted in Chimit-Kolla area to assess their distribution, diversity, and relative abundance in November 2019 to September 2020. Line transect sampling and focus group discussions were used for data collection. Shannon diversity index and Sorenson’s coefficient were used to compute the diversity and habitat utilization of species. The association of species among habitats was tested using the chi-squared test. In the survey, 18 species of medium- and large-sized mammals belonging to the order Artiodactyla (7 species), Carnivora (6 species), Rodentia (1 species), Primates (3 species) and Tubulidentata (1 species) were recorded. The association of mammalian species among the three habitats was not significant ( p > 0.05 ). However, the abundance of mammal species was significantly associated with forest habitats ( p < 0.05 ). There was a significant variation in abundance of medium- and large-sized mammal species observed in the dry season (157, 57.5%) as compared to the wet season (116, 42.5%) (χ2 = 6.17, df = 1, and p = 0.013 ). The most abundant species was olive baboon (Papio anubis), followed by grivet monkey (Chlorocebus aethiops) and crested porcupine (Hystrix cristata). While leopard (Panthera pardus), white-tailed mongoose (Ichneumia albicauda), and aardvark (Orycteropus afer) were the rarest mammalian species recorded. Forest habitat has the highest species diversity (H’ = 2.276) than riverine vegetation and wooded grassland. Mammal species showed a considerable similarity among habitats, and the highest similarity was recorded between forest and wooded grassland (S = 0.8). The study area relatively has considerable numbers of medium- and large-sized mammal species, and urgent conservation action is required to reduce the emerging threats (hunting, charcoal production, agriculture, and investment expansion) and ensure survival of mammal species.

Terrestrial Medium and Large-Sized Mammalian Species Diversity in Michole Community Protected Forest, Southern Ethiopia

Study on medium and large size mammalian species diversity and distribution is important for conservation efforts in the different protected areas of Ethiopia. The study aimed to assess the species diversity of medium and large-sized mammalian fauna between October 2019 and July 2020 in Michole Community Protected Forest, southern Ethiopia. The study was conducted by stratification of the study area into three habitat types riverine forest (3.37 km2), woodland (4.14 km2), and grassland with scattered trees (2.33 km2) based on the vegetation cover. A diurnal transect survey method was implemented to record the mammalian species diversity. A total of 18 representative sample transect lines (six in riverine forest, four in grassland with scattered trees, and eight in the woodland habitats) which varied in length and width were used. A total of 17 species of medium and large-sized mammalian species were identified and recorded in the study area. Accordingly, order Carnivora and Primates constitutes a large proportion of abundance, while order Lagomorpha was the least. Anubis baboon (Papio anubis) was the most abundant species (15.14%) followed by Spotted hyena (12.98%), Porcupine (12.51%), Vervet monkey (10.35%), Common duiker (8.80%), and Giant root-rat (8.65%). The distributions of mammals among the three habitat types were comparable. Riverine forest harbored the highest mammalian diversity index (H’=2.35) followed by the woodland (H’=2.32), and the grassland with scattered trees (H’=2.30), respectively. The greatest species similarity was recorded in woodland (0.902). The study area harbors considerable mammalian species that are threatened by interacting anthropogenic factors. So, urgent conservation measures by concerned sectors are needed to safeguard these animals and their habitat.